1. Field of the Invention
The present invention relates to field of the methods of operating an engine having an after-treatment system that treats exhaust gas from the engine, including adjusting the operation of the engine to increase the temperature of the exhaust gases, and hence of the after-treatment system (ATS). The after-treatment system may comprise a Selective catalytic reduction (SCR) for the reduction of the NOx emissions and/or a Diesel Particulate Filter (DPF) and/or an oxidation catalyst and/or a clean up catalyst.
2. Description of the Prior Art
Internal combustion engines and diesel engines in particular, often include an after-treatment system for treating exhaust gas from the engine.
In order for the ATS to correctly treat the exhaust gases, it must be heated up to the light-off temperature of the SCR catalyst.
Similarly, the DPF regeneration procedure needs to reach a minimum suitable temperature to be carried out. In general, several measures lead to an increase of the ATS temperature.
Therefore, the engine ECUs are programmed to cause a fuel injection amount variation from a normal amount until the ATS reaches the working temperature.
Other techniques have been developed in order to heat up the ATS temperature.
A common result of any of these techniques is the dismissal of the optimal engine working point.
Of course, this in order to reach a better ATS working point leading to a better working point for the overall system comprising the combustion engine and the ATS.
During these heat-up periods, a high amount of fuel is burnt and additional pollution may be produced for both the high amount of fuel burnt and the low efficiency of the ATS.
Combustion engines could be used also in special and/or extreme conditions. For example, the engine could be left running idle or at low power over a long period, in addition, the environment temperature could be critically low.
In such particular conditions, such suitable temperature could never been reached.